Is tikz the easiest way to draw a model like this?

Question

I'm losing my fingers drawing this figure:

Does anybody knows whether tikz is the best way to do that?

Answer 1

This should be all the techniques you need:

Code

\documentclass[parskip]{scrartcl}
\usepackage[margin=15mm]{geometry}
\usepackage{tikz}
\usetikzlibrary{arrows}

\begin{document}

\begin{tikzpicture}[-latex]
\node[draw] (t1) at (0,0) {Twin 1};
\node[draw,circle] (a1) at (-4,1) {A};
\node[draw,circle] (b1) at (2,2) {B};
\draw (a1) -- node[fill=white] {0.42} (t1);
\draw (b1) -- node[fill=white] {0.23} (t1);
\draw[latex-latex] (a1) to[out=45,in=135] node[fill=white] {0.69} (b1);
\end{tikzpicture}

\end{document}

Result